Constant control material feeding mechanism



June 18, 1963 M. WILLS ETAL CONSTANT CONTROL MATERIAL FEEDING MECHANISM 6 H.. M85 e I I 1 NL e ELL mm WML I. .ll 1 A WU h s L 3 I I I I 4U s M1 Y B um J n 1 w I H I n w H M u l L l 1 F June 18, 1963 M. WILLS ETAL CONSTANT CONTROL MATERIAL FEEDING MECHANISM Fiied May 9, 1961 3 Sheets-Sheet 2 IN V EN TORS MflRV/N WILL 5 6 BY JUL/(l6 ALL/5 ATTORNEY June 18, 1963 M. WILLS ET AL 3,094,263

CONSTANT CONTROL MATERIAL FEEDING MECHANISM Filed May 9, 1961 3 SheetsSheet 3 Fig: 6' F T I'ign? INVENTORS MARVIN WILLS 6 By JUL/US ALL/E ATI'OR/VEY United States Patent 9 3,094,263 CONSTANT CONTROL MATERIAL FEEDING MECHANISM Marvin Wills and Julius Allie, Colorado Springs, (3010.; said Allie assignor to said Wills Filed May 9, 1961, Ser. No. 108,806 8 Claims. (Cl. 226-150) This invention relates to stock feeding mechanisms commonly used for feeding material in coiled form to the work-forming member of machines such as a punch press. More specifically, this invention concerns an improved lluidaoperated, constant control, work feeding device for the intermittent advancement of strip material such as steel, brass, copper, paper, mica, rubber, fibre and the like to the cooperating members of a workforming machine.

Generally speaking, the feed mechanism of the prior art and those presently available, whether of the rollfeed type or hitch-feed type, have not satisfactorily solved the problems and requirements incident to the methods and machines of the present day. To enumerate briefly, the available stock feed assemblies cannot be relied upon to provide a continuously accurate feed advancement, thus making necessary the considerable use of pilot holes in the stock. The type of stock clamping devices known to the prior art do not provide a constantly accurate feed because the stock grippers are susceptible to slippage and uneven holds due to the condition of the stock being fed. Neither do the :feed mechanisms of the prior art provide a constant positive control over the material being fed.

It is thus the principal object of the present invention to increase and improve the accuracy and consistency of the intermittent advance type of stock feeding apparatus.

A second principal object of the invention is to permit a lasting, accurate adjustment of the feed length by providing stock clamping means that are unaflected in their clamping accuracy by rough or irregular stock.

A fiurther object of the invention is to exert a positive control over the stock being fed at all times during a feeding cycle.

A further object of the present invention is to provide feeding apparatus which can be loaded or unloaded simply and efliectively.

-A still further object of the present invention is to simplify the setup procedure for applying the feed mechanism to a different job, including the adjustments to be made tor the width and thickness of the material being fed.

Other objects, features, and advantages will be apparent from the following description read in conjunction with the accompanying drawings in which a certain embodiment of the invention is illustrated by way of example.

In the drawings:

FIGURE 1 is a side view of the feed mechanism showing the carriagenrounted, piston-housing cylinder in a cut-away cross section. In the position shown, the limit switch of the fluid valve has just been switched to a position to activate the carriage-mounted, stock gripping means into a clamped position ready for advancement of the stock to the left.

FIGURE 2 is a top view of the feed mechanism showing the slidable carriage inits extreme retrograde positio fi.

FIGURE 3 is a side view of the feed mechanism illustrating the movable cam member which is attached to the reciprocally movable member of the die set in its raised position and the slidable carriage of the feed mechanism in its extreme forward position. As shown and illustrated, the fluid valve has just been switched to deactivate the carriage-mounted stock gripping means and has activated the body-mounted stock gripping means to thereby 3,094,263 Patented June 18, 1963 securely hold the stock in place during the retrograde movement of the carriage.

FIGURE 4 is a front View of the iced mechanism showing the dove-tail slide of the body member on which is mounted the carriage.

FIGURE 5 is a rear view of the feed mechanism.

FIGURE 6 illustrates in detail the fluid valve in vertical cross section and its limit switch together with the adjustable switch actuator shown in solid lines at its lower extreme position, and in the dotted lines in its upper extreme position, and further illustrating the safety brake feature of the limit switch.

FIGURE 7 is a top view of the fluid valve and the switch actuator shown in partial cross section, reference being made to the cross section line 77 in FIGURE 6.

FIGURE 8 is a rear view or the switch actuator and cam member illustrating the adjustable features of the actuator.

Briefly, the present invention contemplates a body member which is generally mounted directly on the die set of a punch press, the body member slidably mounting a reciprocal carriage. Attached to and made a part of the carriage and body member respectively are a pair of fluid actuated stock grippers, each of which include a stationary member and a movable member which cooperate to clamp the stock or work being fed therebetween. Each of the movable members of the stock grippers is actuated to a clam-ping position by a fluid-pressure driven piston, or extension thereof. The pistons are arranged to operate in a timed relation to each other to provide the intermittent feeding of the stock and to exert a positive control over the stock at all times. The piston operation is accomplished by the alternate application of fluid pressure to the said pistons through the use ot a fluid valve, the valve being so constructed and arranged as to direct fluid pressure first to one piston and then to the other with an overlap period in the switching sequence during which pressure is applied. to both pistons. Switching of the fluid valve is eifected by a limit switch and actuator combination, the actuator cooperating in timed relation with force means, which provide retro-grade movement of the carriage relative to the body member. During the retrograde motion of the carriage, the piston of the stock gripper carried by the carriage is deactivated and the said stock gripper does not clamp the stock, but allows tree relative movement between the stock and gripping or clamping members.

During the retrograde motion of the carriage, the fluid valve is in such position as to direct fluid pressure to the piston including in the body-mounted stock gripper, thus providing a positive locking in place of the stock while the carriage stock gripper is moving rearward for another bite on the stock. When the carriage has reached its full rearward travel, due to the cessation of the applied force in that direction, the limit switch actuator is so arranged, as will become more evident as the disclosure continues, as to reverse the valve and direct fluid pressure to the carriage-mounted stock gripper .and release the fluid pressure to the piston of the body-mounted stock gripper. It is to be noted that the application of pressure to one piston is coincident with the application of pressure to the other piston for a short duration of time during the switching sequence in order that the stock will at all times be under positive control.

Second force means are applied to the carriage and urge its movement in a forward direction at such time as the rearwardly directed force is removed, thus while gripping the stock, the carriage advances it into the work forming area of the machine.

It is believed that the general application of the type of device herein disclosed is familiar to those skilled in the art and a detailed description of the machine or machines to which this device can be applied is unnecessary to a full and adequate disclosure thereof; however, for record purposes reference is made to the United States Patents to R. L. Hartwell, No. 1,960,573, and H. E. Dickerman, No. 1,986,479, wherein a full description of the general application and setting of this general type of device is set forth.

Referring now to the drawings in more detail, there is shown generally at in FIGURES 1, 2, and 3, the feed mechanism of the present invention. Forming the base or foundation for the device and a means for attachment of the feed mechanism to the die set of a punch press or the like, is a body member 2 having a front portion thereof machined to a trapezoidal cross section shape forming a dovetail 4, upon which is slidably mounted a carriage 6.

At the rear portion and to one side of the body member 2, and separated from the dovetail portion 4, is an upstanding wall 8 adapted to support a portion of the stock gripping means, specifically a piston-housing cylinder 12 and a spring finger 14.

Similarly situated and in alignment with the upstanding wall 8, integral with the body member 2, is a second upstanding wall 16 integral with the slidably mounted carriage 6. The carriage wall 16 serves, similarly to the body wall 8, to support a portion of a second stock gripping means, specifically a piston-housing cylinder 13 and a carriage-mounted spring finger 20. Rotatably mounted on the upper forward corner of the carriage wall 3 is a steel disk cam follower 22 positioned to co-act with the inclined cam surface 30 of a reciprocally movable member 32, attached to the punch press being fed by the mechanism.

Retrograde movement of the carriage, derived from the downward travel of the cam surface 30, acts to compress a spiral mainspring 24 coiled around the threaded feed adjusting screw 26 which is rigidly attached at one of its ends to the lower portion of the carriage 6. The free end of the feed adjusting screw 26 protrudes through a hole in a supporting ear 28 depending from the side of the body member 2. The said hole is of such large dimension with respect to the diameter of the screw 26 as to permit easy sliding movement for the screw 26 in the hole and of small enough diameter as to bar the mainspring 24 from entering the hole. Thus, the mainspring is abutted between the carriage 6 and the ear 28 of the body member 2. The aforesaid compression and resulting stored energy of the mainspring 24, accumulated during the retrograde movement of the carriage 6, serves to return the carriage to its original forward position as the cam follower 22 moves down the inclined surface 30 of the movable member 32, thereby removing the restraining force heretofore opposing forward movement of the carriage by the spring energy. This spring urged movement of the carriage in a forward direction advances the stock a given distance depending on how far the carriage is permitted to travel before the stop nut 34 abuts the ear 23 of the body member 2 as seen in FIGURE 3. The stop nut 34 is threaded onto the free end of the feed adjusting screw 26 and can be variably located thereon to provide feed distances of small fractions of an inch up to several inches. Once the proper adjustment is made by positioning the stop nut 34-, a lock nut 36 is tightened against it to insure a fixed placement of the stop nut and a constant feed distance.

As best seen in the front and rear views of FIGURES 4 and 5 respectively, the top portions of the carriage 6 and body member 2, together with the upstanding walls 8 and 16 of the body member and carriage and the overhanging piston-housing cylinders 12 and 18, for a semienclosed channel or course through which the stock 40 is trained. The top portions of the carriage and body member are in level relation to one another to secure for the stock a level course over which to travel, as an integral part of the stock gripping means, to be more specifically described subsequently, each of the level top portions of the carriage and body member are provided with raised bosses forming small platforms 41 and 39 against which the spring fingers 20 and 14 can exert a clamping force. To more completely enclose and control the stock 40 as it moves through the said course in the feed mechanism, a lateral stock guide disk 38 is rotatably mounted on an upstanding pin 4-2 secured to a slotted bracket 44 slidably secured with a screw 46 to the mid-section of the body member 2. By sliding the bracket 44 on its slot mounting screw 46, the stock guide can be adjusted to closely control and restrict the possible lateral movements of the stock 40 by confining the said stock between the guide 38 and the walls 8 and 16.

The two stock gripping means, referred to above as mounted on the carriage 6 and the body member 2, are identical in their construction and it will, therefore, be deemed sufiicient to describe only one of them in detail. The piston-housing cylinder 18 is rigidly secured to the support wall 16 of the carriage and a portion thereof overhangs the stock course, as described above. Within the cylinder 18 is housed a reciprocally movable piston 50 having a centrally bored actuating rod 52 depending from the center of the circular piston 50 and integral therewith. Vertically aligned with depending actuating rod 52 is an upwardly extending barrel 54, also centrally bored and integral with the piston 50, protruding through a centrally disposed opening in the top of cylinder 18.

Inside threads on the lower portion of the actuating rod 52 receive the threaded end of a biasing stem 56. Inserted into the aligned bores of the piston barrel 54 and the actuating rod 52, the biasing stem 56 may be screwed so as to extend beyond the lower surface of the actuating rod 52. and thereby bias the spring finger 20 into a lower position for the clamping of thin stock. For stock of greater thickness, an adequate grip is obtained by unscrewing the biasing stem 56 into a retracted position in the actuating rod 52. A lock nut 58 is threaded onto the upper extremity of the stem 56 to lock it at a desired level.

In the embodiment shown and described herein, the fluid contemplated for use to exert an activating pressure on the pistons is air. Other fluids, such as oil, could also be used without a departure from the scope of this invention. To properly seal the air chamber 59 in the cylinders, a rubber O-ring 60 is inserted in a circumferential groove around the periphery of the piston 50, which O-ring expands against the inside wall of the cylinder 18 with sufiicient force to form an air tight seal for the bottom of the air chamber 59. Sealing the top of the chamber 59 is a second O-ring 62 surrounding the piston barrel 54 and disposed in a recessed groove in the cylinder cap 18a.

Completing the movable portion of the stock gripping means is the spring finger 2t) fastened to the carriage by a screw 21. The spring finger 20, as the name suggests, is fabricated from spring steel and exerts an upward pressure on the actuating rod 52 and its piston 50, thus returning the piston to its uppermost position in its chamber within the cylinder 18 when fluid pressure is not applied thereto. The movable end of the spring finger 20 is downwardly bent to exhibit a clearly defined flat surface to contact the top of the feeding stock.

To direct the flow of air pressure to the respective pistons, an air valve, generally designated by numeral 65, is placed at the end of the pressure line coming from a source of air pressure. The valve includes a body member which comprises a base 67 and a valve cap 69 secured to the base 67 by any convenient method known to the art. Situated at the rear of the base 67 are three vertically aligned ports, a centrally located inlet port 71, and two outer outlet ports 73 and 75. To these ports are attached appropriate flexible hose connections which convey pressure to the valve and to the actuating pistons. Interconnecting the ports within the interstices of the valve body are a series of passageways 76 forming air conducting conduits. Included between and as a part of the passageways is a larger cavity 77. Disposed within the cavity 77 is a slidable piston 80 having a thickness less than that of the cavity so as to permit air passage from the input port 71 behind the piston and around one of its ends so as to flow into one of the passageways leading to the output ports 73 and 75. The length of the piston is such as to allow the aforementioned air flow around its one end, while blocking air flow into the passageway at the opposite end of the cavity. During travel from one extreme end position to the other, while the piston 80 is centrally located in the cavity, the passageways to both output ports are open to the flow of air pressure, in this way providing an overlap in the actuation of the two gripping means.

Referring to FIGURE 6, it will be noted in the cross sectional view that the central portion of the valve cap 69 is bored through to permit the escape of exhaust air pressure and also to permit the insertion of the pivoted switch arm 82. The forward facing of the slide piston 80 is slotted to a nominal depth in the direction of the length thereof, the slot being designated as 83. The exhaust slot 83 engages the end opening of one of the passageways 76 which is covered by the piston 80, that is the passageway at the same end of cavity 77 in which the piston is at rest, thus providing communication through the central bore in the valve cap 69 between a pressurized piston cylinder and atmospheric pressure. This communication relieves the pressure above the piston, allowing the spring finger to lift the piston and release the grip on the stock.

Centrally located in the piston face slot 83 is a second slot 85 of smaller length and width than the exhaust slot 83 and adapted to receive the rounded end of the limit switch arm 82. The switch arm 82 is pivotally mounted on a spindle 84 which is journaled at each of its ends in a pair of ears 86 projected from the valve cap 69. Snugly surrounding the switch arm at its free end is a U-shaped bail 88, pivotally mounted on its straight side by the spindle S4. Transverse portion of the bail 88 is spaced apart a small distance from the end of the switch arm to permit relative rotational movement therebetween. Ordinarily the bail 88 and the switch arm 82 move as a single unit, the two members being snap connected by a pair of detents 90 in the switch arm. However, if more than ordinary force were applied to the bail 88 by the switch actuator 95, the detents 90 would slip out of the hole 91 and the bail 88 would rotate out of the way of the actuator 95 without damage to the switch. The two extreme switch positions of the limit switch are portrayed as is the unsnapped position of the bail 88.

As best seen in FIGURES 6, 7, and 8, the switch arm 82 and bail 88 are moved by the switch actuator arm 95 and the outward extending ears 96 and 97 protruding therefrom. As noted, the actuator arm 95 comprises a bracket 98 and two slotted leaves 99 and 100 bolted to the bracket. The adjustment made possible by the slotted leaves 99 and 100 permits varying operational distances to be selected between the cars 96 and 97, thus permitting wide variation in the stroke distance of the machine member to which the bracket 98 and the cam member 32 are attached.

As noted in the drawings, the bleed-shutoff valve is inserted in the pressure input line so that the pressure into the valve can be terminated and any remaining pressure in the valve or pistons can be bled off. This function permits the deactuation of both stock grippers and the stock may be removed from the feed mechanism or new stock may be added.

Having thus described the several useful and novel features of the feed mechanism of the present invention in connection with the accompanying drawings, it will be seen that vthe many worthwhile objectives for which it was designed have been achieved. Although but a few of the several possible embodiments of the invention have been illustrated and described herein, we realize that cer- 6. tain additional modifications may well occur to those skilled in the art within the broad teaching hereof; hence, it is our intention that the scope of protection afforded hereby shall be limited only insofar as said limitations are expressly set forth in the appended claims.

We claim:

1. A material feeding mechanism for the controlled feeding of indefinite lengths of stock to a machine, wherein such stock is worked by a reciprocably moving member comprising in combination: a body member having a dove-tail slide on one end thereof and an upstanding support on the other end thereof, and said body member forming a rear stock supporting platform; a carriage slidably mounted on the dove-tail slide of the said body member and having a front stock supporting platform thereon, said carriage further comprising, a support member upstanding from and integral with one side of said carriage, and a cylindrical shaped air cylinder secured to said support member and overhanging said front stock supporting platform; a cam follower rotatably mounted on said support member; a first piston housed by said cylinder and having a downwardly extended actuating rod adapted to emerge through a centrally located opening in said cylinder; and a stock-gripping spring finger attached at one of its ends to the said support member and having its free end disposed between said front stock supporting platform and the depending actuating rod of said first piston; a second cylindrical shaped air cylinder, said second cylinder secured to the upstanding support on the said body member and overhanging the rear stock supporting platform; a second piston, said second piston housed by said second cylinder and having a downwardly extended actuating rod adapted to emerge through a centrally disposed opening in the said second cylinder; a rear stock-gripping spring finger attached at one of its ends to the said body member and having its free end disposed between said rear stock supporting platform and the depending actuating rod of said second piston; a feed adjusting screw secured at its one end to said carriage, a spiral spring surrounding said screw and abuttcd between said carriage and said body member; a plurality of stop nuts threaded to the free end of said screw and separated from the spiral spring by a portion of the body member; a pressure source; an air valve, said valve comprising a valve body, a plurality of outlet ports, an inlet port, an exhaust port, air conducting passageways in said valve body inter-connecting said ports, a slide piston disposed within a portion of said passageways and adapted to divert and direct air flow to and from the said ports, a trip lever pivotally mounted on the valve body and operably connected to the slide piston; a flexible tubing connecting said valve body outlet ports with the first and second cylinders, a cam, a Valve trip arm mounted on said cam, said cam attached to the reciprocally moving member of machine which the feeding mechanism serves.

2. In an air operated stock feeding device for the intermittent feeding of stock to a machine having two cooperating and relatively movable work forming members, the combination comprising; a body member having a slide portion on one end thereof; a carriage slidably mounted on the slide portion of the said body member; adjustable guide means movably mounted on said body member and forming a channel guide for stock moving across the body member and carriage; a plurality of stock gripping means, at least one of said means mounted on said carriage and at least one of said means mounted on the said body member, said stock gripping means comprising a platform over which the stock is directed, an upwardly biased finger having a stock engaging surface disposed and adapted to cooperate with said platform to clamp the stock therebetween, a fiuid actuated, reciprocally movable piston having a depending actuating rod normal' to the plane of the stock, said actuating rod engaging the said finger and operating to force said finger into clamping engagement with the stock When the piston is actuated downward, a cylinder housing said piston and actuating rod and providing an opening for the projection of the actuating rod; a fluid valve, said valve including a valve body, a fluid inlet port, a plurality of fluid outlet ports, an exhaust port, fluid conducting passageways, said passageways defining inter-connecting conduits between said ports in said valve body, a slide piston disposed in said passageways and adapted to direct the fluid flow therethrough, and switch means operably connected to said piston for changing the position thereof; fluid conducting conduits inter-connecting the cylinders of the said stock gripping means with the outlet ports of the said valve; and feed means for advancing the stock a predetermined distance, said means including a feed adjusting screw rigidly attached at one end thereof to the said carriage, resilient biasing means interconnecting said carriage and said body member and adapted to maintain maximum separation along the longitudinal axis of the stock of the carriage mounted stock gripping means and the body mounted stock gripping means, and feed adjusting stop means carried by the free end of said feed adjusting screw, said stop means positioned so as to abut a surface of the said body member when the carriage has advanced to a predetermined separation from the body mounted stock gripping means; and means attached to the movable member of the said machine for tripping the valve switch means and for forcing said carriage longitudinally along the body slide portion against the force of the biasing means.

3. In an air operated stock feeding device for the intermittent feeding of stock to a machine having two cooperating and relatively movable work forming members, the combination comprising; a body member having a slide portion on one end thereof; a carriage slidably mounted on the slide portion of the said body member; means attached to said body member and forming a course over which the stock is directed; a plurality of stock gripping means, at least one of said means mounted on said carriage and at least one of said means mounted on the said body member, said stock gripping means comprising, a pair of relatively movable clamping members, a piston reciprocally movable along the axis normal to the stock, means attached to said piston for engaging one of said movable clamping members, and a cylinder housing said piston; a fluid valve for directing fluid pressure to the said pistons for actuating same; conduit means interconnecting said cylinders and said fluid valve; switch means operably interconnecting said valve and the movable member of the said machine; and first and second force means for reciprocally moving said carriage to provide advancement of the stock, said first force means including a cam attached to the movable member of the said machine, a cam follower mounted on said carriage, said cam positioned to engage said cam follower, said second force means including a biasing means interconnecting said carriage and body member and adapted to force the carriage diametrically opposite to the direction of force applied by said first force means, and stop means adjustably secured to said carriage for limiting the travel of said carriage which is produced by the second force means.

4. Material feeding mechanism for the feeding of indefinite lengths of stock to a machine having relatively movable reciprocating Work forming members, comprising in combination; a body member; a carriage slidably mounted on the said body member; course forming means attached to said body member over which the stock is directed; a pair of stock gripping means, one of said stock gripping means being secured to said carriage, the other of said stock gripping means being secured to said body member, said stock gripping means comprising, a pair of relatively movable clamping members, piston means reciprocally movable along an axis normal to the stock member of the machine; and first and second force means for reciprocally moving said carriage to provide advancement of stock, said first and second force means being directed to and applied on the said carriage.

5. The combination of claim 4 wherein the fluid directing means comprises; a fluid valve;

a pair of output conduits interconnected respectively between each of the housing cylinders and the said fluid valve;

an input conduit interconnecting a source of fluid pressure and the fluid valve;

the said fluid valve including;

a body member having fluid transporting passageways interconnecting the output and input conduits;

a piston slidably disposed within said passageways and adapted for movement therein between two extreme positions, whereby one of said positions prevents passage of fluid from the input to one of said outputs, said piston and passageways being sized and constructed so as to establish communication between the input and both of said outputs when the piston is mid-way between its two extreme positions;

switch means mounted on the body member and operably connected to the piston for actuating the piston into one of its two extreme positions; and

exhaust means communicating with the passageways to provide pressure relief to one of the output conduits.

6. The combination of claim 5 wherein the switch means comprise a stem pivotally mounted at its midsection, one end thereof inserted into a cooperating recess in the said valve piston and the other end thereof protruding from the valve body in a substantially normal relation thereto, a bail member enclosing said stem on two of its sides, said bail member pivotally mounted for rotational movement with said stem as one unit, and override fastening means formed within said stem and said bail for rigidly connecting the stem and bail for integral movement, whereby a certain predetermined force will cause a disconnection of the stem and bail.

7. The combination of claim 4 wherein said fluid directing means includes valve means, a pair of output conduit means connecting said valve forming means and said pistons, and switch means attached to said valve forming means for directing fluid pressure into a designated one of the output conduit means.

8. The combination of claim 7, and further including a switch actuator operably connected to the said first force means and adapted to operate the said switch means in timed relation with the application of force by the first force means to the said carriage.

References Cited in the file of this patent UNITED STATES PATENTS 2,622,874 Haller Dec. 23, 1952 2,624,659 Haug et a1. Jan. 6, 1953 2,811,397 Cline Oct. 29, 1957 2,863,659 Chuy Dec. 9, 1958 2,929,626 Weymouth Mar. 22, 1960 3,039,833 Parkas June 19, 1962 FOREIGN PATENTS 578,936 Germany May 2, 1930 1,124,738 France Oct. 16, 1956 

4. MATERIAL FEEDING MECHANISM FOR THE FEEDING OF INDEFINITE LENGTHS OF STOCK TO A MACHINE HAVING RELATIVELY MOVABLE RECIPROCATING WORK FORMING MEMBERS, COMPRISING IN COMBINATION; A BODY MEMBER; A CARRIAGE SLIDABLY MOUNTED ON THE SAID BODY MEMBER; COURSE FORMING MEANS ATTACHED TO SAID BODY MEMBER OVER WHICH THE STOCK IS DIRECTED; A PAIR OF STOCK GRIPPING MEANS, ONE OF SAID STOCK GRIPPING MEANS BEING SECURED TO SAID CARRIAGE, THE OTHER OF SAID STOCK GRIPPING MEANS BEING SECURED TO SAID BODY MEMBER, SAID STOCK GRIPPING MEANS COMPRISING, A PAIR OF RELATIVELY MOVABLE CLAMPING MEMBERS, PISTON MEANS RECIPROCALLY MOVABLE ALONG AN AXIS NORMAL TO THE STOCK AND ADAPTED TO ENGAGE ONE OF THE RELATIVELY MOVABLE CLAMPING MEMBERS, AND A CYLINDER HOUSING SAID PISTON MEANS; MEANS DIRECTING FLUID PRESSURE TO THE SAID PISTON MEANS FOR ACTUATING THE SAME; ACTUATOR ARM MEANS INTERCONNECTING SAID FLUID DIRECTING MEANS AND THE SAID MOVABLE MEMBER OF THE MACHINE; AND FIRST AND SECOND FORCE MEANS FOR RECIPROCALLY MOVING SAID CARRIAGE TO PROVIDE ADVANCEMENT OF STOCK, SAID FIRST AND SECOND FORCE MEANS BEING DIRECTED TO AND APPLIED ON THE SAID CARRIAGE. 